Process of recovering alkali and glycerine from spent soap-lye



(No Model.) I

E. D. MELLEN. PROCESS OP REGOVBRING ALKALI AND GLYCERINE FRUM SPENT SOAP LYE.

120.422.140. Patented P61025, 1890.

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UNITED STATES PATENT OFFICE.

. EDWIN D. MELLEN, OF CAMBRIDGE, MASSACHUSETTS.

PROCESS OF RECOVERING ALKALI AND GLYCERINE FROM SPENT SOAP-LYE.

SPECIFICATION forming part of Letters Patent No. 422,140, dated February 25, 1890.

Application filed September 20, 1889. Serial No. 324,544. (No specimens.)

.sectional elevation, a form of apparatus to be employed in carrying out my process.

My invention consists of an improved pro` cess for the ready and cheap recovery of both alkali and glycerin@ from the waste lyes in soapmaking, the details of which process are hereinafter given.

It is well known that waste lyes from soap- Amaking commonly contain alkali, glycerine, and salt. In the processes ordinarily employed hitherto for the recovery of the glycerine the alkali is entirelylost or imperfectly recovered at great expense, while the presence of salt renders the recovery of the glycerine very difficult.

My process consists, rst, in the use of an excess of caustic alkali, preferably soda, in

the treatment of the soap-stock, sufficiently larger than the amount ordinarily required to saponify the fat, so that the soap may be be precipitated by the alkali without the addition of salt. To do this I preferably proceed in the following way: The tallow or other soap stock containing glycerine is melted in an ordinary soap-kettle with water and a solution of caustic soda of 30O Baume added in the usual proportion, and the soap ,boiled in the common way; but a quantity of lthe tower.

I proceed as follows: The lyes are evapoe rated to preferably about one-seventh of the volume of lye as taken from the soap, or until they contain about fifty per cent. of glycerine. They are then pumped through a pipe G into a cylindrical tower A, consisting,

preferably, of a series of cylinders superimposed one upon another in the manner illustrated, and containing at intervals perforated shelves a of the shape of aspherical segment. The purpose of this apparatus isfor the satu' ration of the lyes with carbonio-acid gas.

C is the gas-pipe entering the bottom of the tower and terminating within it in the rose or perforated circular pipe B.

D is lapump or blower of any approved construction for delivering a constant quantity of gas through the pipe C and rose B into the concentrated soap-lyes contained in I preferably generate the gas to be used for this purpose by the action of rosin or fatty acids upon bicarbonate of soda; but the gas may be obtained in any desired manner, or furnace-gases may be employed.

In the drawing, the gas-pipe E, leading to the pump or blower, connects `with the two pipes K and L, one of which leads to a gasgenerator and the other to a furnace, so that bythe cocks k and Z either furnace-gas or carbonic-acid gas obtained directly from the generator may be pumped'into the tower A and forced through the soap-lyes, thoroughly saturating the same.

evaporated, and the result is marketable as a crude glycerine, or it can be further purified by distillation with steam or hot air.

I claimum By this treatmentl the can bonate and caustic soda are transformed into ing the concentrated lye thus obtained with carbonio-acid gas, whereby the alkali is separated as a bicarbonate and glycerine `left in solution, substantially as set forth.

In witness whereof I have hereunto set my hand.

EDNVIN D. MELLEN. WVitn esses WM. B. H. DoWsE, ALBERT E. LEACH. 

